In a medium bowl, toss shrimp with 1/4 cup dressing. Season with salt and pepper and grill until bright pink and just cooked through, about 4-6 minutes. Blanch snow peas in salted boiling water for 1 minute, just until they turn bright green. Drain and place in ice water to cool. Remove from water and pat dry.

In a large bowl, toss snow peas, spinach, mint, mango and pepper with remaining 1/2 cup dressing. Season with salt and pepper and divide among 4 plates. Top with shrimp, sprinkle with scallions and serve with additional dressing as desired.